firmware/target/coldfire/kernel-coldfire.c

   1 /***************************************************************************
   2  *             __________               __   ___.
   3  *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
   4  *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
   5  *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
   6  *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
   7  *                     \/            \/     \/    \/            \/
   8  * $Id$
   9  *
  10  * Copyright (C) 2002 by Björn Stenberg
  11  *
  12  * This program is free software; you can redistribute it and/or
  13  * modify it under the terms of the GNU General Public License
  14  * as published by the Free Software Foundation; either version 2
  15  * of the License, or (at your option) any later version.
  16  *
  17  * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
  18  * KIND, either express or implied.
  19  *
  20  ****************************************************************************/
  21 #include "config.h"
  22 #include "system.h"
  23 #include "kernel.h"
  24 #include "panic.h"
  25
  26 void tick_start(unsigned int interval_in_ms)
  27 {
  28     unsigned long count;
  29     int prescale;
  30
  31     count = CPU_FREQ/2 * interval_in_ms / 1000 / 16;
  32
  33     if(count > 0x10000)
  34     {
  35         panicf("Error! The tick interval is too long (%d ms)\n",
  36                interval_in_ms);
  37         return;
  38     }
  39
  40     prescale = cpu_frequency / CPU_FREQ;
  41     /* Note: The prescaler is later adjusted on-the-fly on CPU frequency
  42        changes within timer.c */
  43
  44     /* We are using timer 0 */
  45
  46     TRR0 = (unsigned short)(count - 1); /* The reference count */
  47     TCN0 = 0; /* reset the timer */
  48     TMR0 = 0x001d | ((unsigned short)(prescale - 1) << 8);
  49            /* restart, CLK/16, enabled, prescaler */
  50
  51     TER0 = 0xff; /* Clear all events */
  52
  53     ICR1 = 0x8c; /* Interrupt on level 3.0 */
  54     IMR &= ~0x200;
  55 }
  56
  57 void TIMER0(void) __attribute__ ((interrupt_handler));
  58 void TIMER0(void)
  59 {
  60     /* Run through the list of tick tasks */
  61     call_tick_tasks();
  62
  63     TER0 = 0xff; /* Clear all events */
  64 }